A gas turbine generally includes a compressor section, a combustion section having a combustor, and a turbine section. The compressor section progressively increases the pressure of the working fluid to supply a compressed working fluid to the combustion section. The compressed working fluid is routed through one or more fuel nozzles that extend axially within a forward, or head, end of the combustor. A fuel is combined with the flow of the compressed working fluid to form a combustible mixture. The combustible mixture is burned within a combustion chamber to generate combustion gases having a high temperature, pressure, and velocity. The combustion chamber is defined by one or more liners or ducts that define a hot gas path through which the combustion gases are conveyed into the turbine section. In a can-annular type combustion system, multiple combustion cans (each having its own fuel nozzle(s) and liner) produce combustion gases that drive the turbine section.
The combustion gases expand as they flow through the turbine section to produce work. For example, expansion of the combustion gases in the turbine section may rotate a shaft connected to a generator to produce electricity. The turbine may also drive the compressor by means of a common shaft or rotor.
In the combustor section, the fuel nozzles may operate solely on gaseous fuel, solely on liquid fuel, or simultaneously on gaseous fuel and liquid fuel. In many instances, a power-generation plant may experience sustained periods when it is necessary to operate using only liquid fuel.
One challenge commonly associated with liquid fuel operation is the tendency of the liquid fuel to coke within the fuel nozzle at temperatures that are only moderately elevated over ambient temperatures and significantly below the flame temperature within the combustion chamber. Another challenge with liquid fuel nozzles is designing the liquid fuel injection ports to produce a uniform spray pattern, such that the liquid fuel is quickly atomized and combusted. An associated challenge is locating the fuel nozzle properly within the combustor head end to prevent the liquid fuel spray from reaching the combustor liner, where coking may occur and lead to thermal stress. Additionally, most liquid fuel nozzles rely on a single liquid fuel circuit, which provides limited flexibility in the operation of the liquid fuel nozzle. Finally, the tip of the liquid fuel cartridge must be cooled to mitigate thermal stresses.
Therefore, an improved liquid fuel cartridge for delivering a liquid fuel to a combustion chamber is needed in the industry.